I am looking for a new player which has replaceable batteries preferably AA or AAA and an sd slot. I currently have the Treckstor Ibeat extension which can use 8gb sd cards. Problem is that some of the buttons are becoming hard to use and the player dont sound to good with my new head phones philips she9850 (some buzzing and noise on changing tracks)

Anyone know of any such players? I have not been able to find any but have been considering getting a cheap mobile phone with mp3 playback but have no idea what they would sound like.

You could also grab a soldering iron, buy some parts and make your own. I'm sure there are "kits" out there.

Then just make your own AA or AAA bat supply. With NiMH you do not have the issue of Lith's where you gotta have protection circuits and ventilation holes etc.NiMHs are pretty darn safe. (they can overheat if charged wrong and "melt", but they won't go "boom" like Lith's can.)

Also, Alkaline AA or AAA's can be plopped in if the rechargeable's are drained and you can't wait.Not to mention the fact that AA or AAA can be found almost in any shop/store.

Heck, maybe someone on HA would be willing to built it for you for a few bucks.Using a Raspberry Pi or some other "Stick PC" would be hilarious and cool as you'd have one of the most powerful pocket players possible. (and potentially support any file format you'd like, and the bonus of being able to hook it up to a HiFi, or a TV to play video).

You could also grab a soldering iron, buy some parts and make your own. I'm sure there are "kits" out there.

That is tough though since you'll need a minimum of 3 and possibly 4 AA or AAA batteries to reach the minimum voltage needed to power on most players. Well that or you'll have to build in a DC to DC power supply to upconvert to the right voltage. It can be done, but you'll probably end up with something that stretches the definition of "portable".